conan: Conan fails to detect the compiler although `CC` and `CXX` are set

Environment details

Operating System+version: ubuntu-22.04
Compiler+version: 13.1.0
Conan version: 2.0.9
Python version: 3.11.4

Steps to reproduce

I am creating a Conda package of my software, as part of a Github C/I workflow. My software depends on other software (e.g.: Boost). For dependencies for which there isn’t a Conda package available I use Conan to install them.

Here is the idea, scattered over the various files (.github/workflows/linux-conda.yml, environment/conda/build.sh):

Create a Conda environment
Install the boa Conda package builder and execute: conda mambabuild environment/conda --override-channels --channel conda-forge

Then build.sh is executed which includes:

conan profile detect                                                                                             
conan install . \                                                           
    --profile=default \                                                                                          
    --settings:host compiler.cppstd=17 \                                                                         
    --settings:build compiler.cppstd=17 \                                                                        
    --settings:build build_type=Release \                                                                        
    --build=missing \                                                                                            
    --output-folder=build

This results in an error (see log below). Conan is not able to correctly detect the compiler. The CC and CXX variables are set, so I would expect that those are used to detect the compiler.

I tried passing in the compiler explicitly, when calling conan install, using --setting compiler=$CXX, but that failed with ERROR: 'settings.compiler' value not defined. Maybe because the whole compiler section is missing from the profile?

I think this is a bug, given that the compiler is installed and pointed to by the standard variables. If not, then my question is how to get Conan to detect the compiler correctly in this situation.

I use the same conan commands to install Conan packages outside of the Conda build environment (on Linux, macOS, Windows), and those work fine. It seems that the Conda build environment is confusing Conan. Maybe because of the atypical setting of CC and CXX?

Logs

2023-08-24T16:10:09.7983374Z CC and CXX: /usr/share/miniconda/envs/test/conda-bld/lue_1692893106258/_build_env/bin/x86_64-conda-linux-gnu-cc, /usr/share/miniconda/envs/test/conda-bld/lue_1692893106258/_build_env/bin/x86_64-conda-linux-gnu-c++ 
2023-08-24T16:10:09.7984827Z ERROR: Not able to automatically detect '/usr/share/miniconda/envs/test/conda-bld/lue_1692893106258/_build_env/bin/x86_64-conda-linux-gnu-cc' version
2023-08-24T16:10:09.7985898Z No compiler was detected (one may not be needed)
2023-08-24T16:10:09.7986712Z WARN: This profile is a guess of your environment, please check it.
2023-08-24T16:10:09.7987819Z WARN: The output of this command is not guaranteed to be stable and can change in future Conan versions.
2023-08-24T16:10:09.7988301Z WARN: Use your own profile files for stability.
2023-08-24T16:10:09.7988673Z Saving detected profile to /home/runner/.conan2/profiles/default
2023-08-24T16:10:09.8382941Z + conan install . --profile=default --settings:host compiler.cppstd=17 --settings:build compiler.cppstd=17 --settings:build build_type=Release --build=missing --output-folder=build
2023-08-24T16:10:10.1836158Z ERROR: 'settings.compiler' value not defined

Somewhat later on in the log:

2023-08-24T16:10:10.3898835Z Detected profile:
2023-08-24T16:10:10.3899230Z [settings]
2023-08-24T16:10:10.3899457Z arch=x86_64
2023-08-24T16:10:10.3899668Z build_type=Release
2023-08-24T16:10:10.3900101Z os=Linux

About this issue

Original URL
State: closed
Created 10 months ago
Reactions: 1
Comments: 17 (9 by maintainers)

Most upvoted comments

@memsharded I think the problem is this logic here:

command = cc or cxx
# ...
if "gcc" in command or "g++" in command or "c++" in command:
  gcc, gcc_version, compiler_exe = _gcc_compiler(command)
  if platform.system() == "Darwin" and gcc is None:
      output.error("%s detected as a frontend using apple-clang. "
                   "Compiler not supported" % command)
  return gcc, gcc_version, compiler_exe

In a conda environment, the CC and CXX variables point to /opt/conda/envs/<env name>/bin/x86_64-conda-linux-gnu-cc and /opt/conda/envs/<env name>/bin/x86_64-conda-linux-gnu-c++ and command ends up being /opt/conda/envs/<env name>/bin/x86_64-conda-linux-gnu-cc and thus _gcc_compiler(command) is never called.

A possible fix is:

if "cc" in command or "g++" in command or "c++" in command:
    # ...

I put up a PR as an example.

hansenms on Feb 13, 2024

I will try to find out what is going on.

kordejong on Aug 26, 2023